moby--moby/pkg/listenbuffer/buffer.go

/*
   Package to allow go applications to immediately start
   listening on a socket, unix, tcp, udp but hold connections
   until the application has booted and is ready to accept them
*/
package listenbuffer

import "net"

// NewListenBuffer returns a listener listening on addr with the protocol.
func NewListenBuffer(proto, addr string, activate chan struct{}) (net.Listener, error) {
	wrapped, err := net.Listen(proto, addr)
	if err != nil {
		return nil, err
	}

	return &defaultListener{
		wrapped:  wrapped,
		activate: activate,
	}, nil
}

type defaultListener struct {
	wrapped  net.Listener // the real listener to wrap
	ready    bool         // is the listner ready to start accpeting connections
	activate chan struct{}
}

func (l *defaultListener) Close() error {
	return l.wrapped.Close()
}

func (l *defaultListener) Addr() net.Addr {
	return l.wrapped.Addr()
}

func (l *defaultListener) Accept() (net.Conn, error) {
	// if the listen has been told it is ready then we can go ahead and
	// start returning connections
	if l.ready {
		return l.wrapped.Accept()
	}
	<-l.activate
	l.ready = true
	return l.Accept()
}